tag 24629 notabug thanks On 10/06/2016 02:48 PM, Norbert Kiesel wrote: > Hi, > > it's been ages that I actually wanted to produce a "classic" diff, and > I don't think I'm alone in that. Yet, I still have to remember to add > `-u` every time I invoke `diff`. > > I understand changing the default is controversial. But perhaps even > using "classic" as default unless POSIXLY_CORRECT is set.
I think you said that backwards, and are proposing that diff would output -u format by default, and ed script format if POSIXLY_CORRECT is set. At any rate, I'm not a big fan of the idea; POSIXLY_CORRECT should control an absolute bare minimum of changes (only where we intentionally differ from POSIX as in incompatible extension), as you still risk breaking many scripts (most of which intentionally don't sent POSIXLY_CORRECT). > > But we should be able to support a GNU_DIFF_FORMAT environment > variable that sets the default format, no? No. We've already learned, from sad experience, that environment variables that affect default behavior are VERY prone to breaking existing scripts that aren't aware of the new environment variable needing to be removed before getting the output they are used to. In fact, existing GNU programs have been actively trying to move away from this paradigm (observe the treatment of GREP_OPTIONS in grep). Environment variables that affect non-default output, such as LS_COLORS, are less problematic - except that then they aren't the default so it still doesn't help your stated use case of getting the new behavior by default. > > I could send a patch, but first want to understand if that would have > any chance of being applied. Probably not worth it. As such, I'm tagging this as not a bug in the database, although you should feel free to add further comments to the thread. > > </nk> > > P.S.: I know I could write my own little wrapper script/alias/shell > function, but that all seems dirty in one way or another. --nk Actually, that IS what we recommend. If you have a particular way that a tool behaves best for you, then the BEST thing to do IS to write a wrapper script which adds the appropriate options, and put that wrapper script first on your PATH for interactive operation. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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